Electrophoretic device having an opening

ABSTRACT

An electrophoretic display device of the present invention is formed of a first substrate, a second substrate, and microcapsules which are accommodated between these substrates and which contain an electrophoretic dispersion, wherein each of the microcapsules has an opening in at least a part thereof.

This application is a divisional patent application of U.S. Ser. No.10/224,635 filed Aug. 19, 2002, claiming priority to JP 2001-249561filed Aug. 20, 2001 and JP 2002-236516 filed Aug. 14, 2002, all of whichare hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Technical Field of the Invention

The present invention relates to electrophoretic devices andmanufacturing methods therefor, and more specifically, relates to anelectrophoretic device in which an electrophoretic dispersion containinga dispersion medium and electrophoretic particles is accommodatedbetween electrodes opposing each other.

In addition, the present invention relates to various electronicapparatuses each provided with an electrophoretic display deviceincorporating the above electrophoretic device.

2. Description of the Related Art

Hitherto, concerning electrophoretic devices in which an electrophoreticdispersion containing a dispersion medium and electrophoretic particlesis accommodated between a pair of electrodes, application thereof toelectrophoretic display devices has been known in which change indistribution of the electrophoretic particles caused by a voltageapplied between the pair of substrates is used. FIG. 3(a) is a viewshowing the general structure of an electrophoretic display device towhich an electrophoretic device is applied.

This electrophoretic display device 20 is composed of an electrode 3formed on a first substrate 1, a transparent electrode 4 formed on asecond substrate 2, an electrophoretic dispersion 10 filled between theelectrode 3 and the transparent electrode 4, and a spacer 7 forpreventing this electrophoretic dispersion 10 from flowing out. Thisfigure shows a cross-section of one pixel of the display device.

The electrophoretic dispersion 10 is composed of a liquid-phasedispersion medium 6 and electrophoretic particles 5 dispersed in thisliquid-phase dispersion medium 6. In addition, the liquid-phasedispersion medium 6 and the electrophoretic particles 5 are colored indifferent colors from each other.

To this electrophoretic display device 20, voltage sources 9 a and 9 b,which apply voltages in the direction opposite to each other, areconnected via a switch 8. That is, the electrode 3 is connected to oneend of each of the voltage sources 9 a and 9 b, and the electrode 4 isconnected to the other end of each of the voltage sources 9 a and 9 bvia the switch 8. When connection is formed as described above, byswitching the switch 8, the direction of a voltage to be applied can bechanged. By changing the direction of a voltage to be applied, theelectrophoretic particles can be gathered at a desired electrode side,thereby performing a desired display.

That is, when the electrophoretic particles 5 are positively charged, asshown in (b) of the same figure, by applying a voltage of the voltagesource 9 a, the electrophoretic particles 5 can be gathered at thetransparent electrode 4 side which is disposed close to an observer. Inthe state described above, the observer can view the color of theelectrophoretic particles 5. On the other hand, as shown in (c) of thesame figure, by applying a voltage of the voltage source 9 b, theelectrophoretic particles 5 can be gathered at the electrode 3 sidewhich is disposed far from the observer. In the state described above,the observer views the color of the liquid-phase dispersion medium 6.When the electrophoretic particles 5 are negatively charged, the movingdirection of the particles is opposite to that described above.

As described above, when the structure shown in FIG. 3(a) is employed,since two types of colors can be displayed in accordance with thedirection of a voltage to be applied, an electrophoretic display devicecapable of displaying a desired image can be realized when the structureshown in the figure is disposed in every pixel.

In addition, an electrophoretic device having the structure in which anelectrophoretic dispersion is enclosed in microcapsules has been known.When the device is thus formed, agglomeration of the electrophoreticparticles and adhesion thereof to electrodes can be dissolved, and atthe same time, handling of the dispersion system can be significantlyimproved during assembly.

However, in the case in which an electrophoretic dispersion is enclosedin microcapsules, gaps are formed between the capsules since themicrocapsule has a spherical shape, and wall films of the microcapsulesare not completely transparent, resulting in decrease in image contrast.

As means for solving the problems described above, for example, therehas been a known technique for deforming microcapsules into anon-spherical shape. However, even when this technique is employed, itis difficult to totally eliminate gaps formed between the microcapsules,and the problem of presence of the microcapsule wall films cannot bedissolved.

The present invention was made in order to solve the shortcomings of thetraditional technique described above, and a first object thereof is toprovide an electrophoretic device and a manufacturing method therefor,in which a dispersion system is easily handled during assembly, andimage contrast can be significantly improved.

A second object of the present invention is to provide an electronicapparatus incorporating a display device, in which image contrast can besignificantly improved even when the display device is anelectrophoretic display device.

SUMMARY OF THE INVENTION

In order to solve the problems of the traditional techniques describedabove and to achieve the first object described above, anelectrophoretic device of the present invention comprises

a first substrate;

a second substrate opposing the first substrate; and

a plurality of capsules which are provided between the first substrateand the second substrate and which contain a dispersing medium andelectrophoretic particles;

wherein the capsules each have an opening formed in at least a partthereof.

According to the structure as described above, since the opening isformed in at least a part of the capsule, decrease in image contrastcaused by gaps formed between the capsules and the capsule wall filmscan be dissolved.

In the case described above, the capsules may have an average volumeparticle diameter of approximately 5 to 300 μm. When the particlediameter is less than 5 μm, since the layer of a colored dispersionmedium becomes thin, satisfactory contrast may not be obtained in somecases.

When the particle diameter is more than 300 μm, mechanical strengths ofthe capsule may be decreased, or since it becomes necessary to increasea driving voltage applied between the electrodes, increase in runningcost may occur in some cases.

In addition, the capsule wall film may have a thickness of approximately0.1 to 5 μm. When the thickness is less than 0.1 μm, satisfactorymechanical strengths may not be obtained in some cases, and when thethickness exceeds 5 μm, the transparency of the wall film is decreased,and hence the contrast may be decreased in some cases.

Furthermore, the content of the capsules in a resin composition (coatingagent) may be set in the range from 30 to 80 wt %. When the content isless than 30 wt %, voids are formed between the capsules, and hencedecrease in contrast or display defects may occur in some cases. Inaddition, when the content is more than 80 wt %, agglomeration of thecapsules occurs in the resin composition, and hence coating defects,damages to the capsules, or display defects may occur in some cases.

The electrophoretic device of the present invention may further comprisea binding agent around the peripheries of the capsules. In particular,the binding agent is characterized in having one or more features amongtransparent, adhesive, plastic, flexible, and insulating properties. Byusing the binder having the features mentioned above, the image contrastcan be further improved.

In addition, in the electrophoretic device of the present invention, anopening portion formed in each of the capsules is in contact with atleast one of the first substrate and the second substrate. In this case,the substrate in contact with the opening portions serves as lidstherefor, and hence the dispersion medium and the electrophoreticparticles are prevented from flowing out from the capsules. In addition,in particular, when the openings faces in the direction parallel to thatof an electric field in which the electrophoretic particles are moved,resistance components or capacitance components in voltage applicationcan be removed or decreased, and hence superior efficiency can beobtained. That is, the dielectric capsule wall films may function as aresistance component or a capacitance component; however, when theopening portions of the capsules are formed in the direction parallel tothat of the electric field, the resistance component or the capacitancecomponent is reduced, and hence voltage application can be effectivelyperformed.

In the electrophoretic device of the present invention, the diameter ina perpendicular direction with respect to the first substrate and thesecond substrate may be smaller than that in the horizontal direction.In particular, the diameter in the perpendicular direction may be set toapproximately 15 to 80 μm, and the diameter in the horizontal directionmay be set to approximately 50 to 200 μm.

In the electrophoretic device of the present invention, the firstsubstrate has light transmissive properties, and the opening portionsare provided at the first substrate side. In addition, in particular,openings may not be provided in parts of the capsules at the secondsubstrate side. Accordingly, for example, when the first substrate sideis used as a viewing side, the visibility of the electrophoretic deviceis improved. In particular, by forming the opening portions at theviewing side, the gaps between neighboring capsules disposed at theviewing side are unlikely to be formed, conventional defects such ascontrast decrease by light leakage caused by the presence of the gapscan be avoided or suppressed.

In addition, a first electrode may be formed at the internal surfaceside of the first substrate, and an insulating film may be formedbetween the first electrode and the opening portions of the capsules. Inthis case, since the electrophoretic particles are not brought intodirect contact with the first electrode, defects such as adhesion of theelectrophoretic particles to the electrode can be avoided or suppressed.Furthermore, a color layer may be further provided between the openingportions and the first substrate. Accordingly, color display having highcolor purity can be realized.

Next, to achieve the objects described above, according to the presentinvention, an electrophoretic device having scanning lines, signallines, and switching elements provided at respective intersectionstherebetween, comprises:

a first substrate;

a second substrate which is disposed opposing the first substrate and onwhich the switching elements are provided; and

capsules which are provided between the first substrate and the secondsubstrate and which contain a dispersion medium and electrophoreticparticles;

wherein the capsules each have an opening formed in at least a partthereof.

According to the electrophoretic device as described above, the firstsubstrate side on which the switching elements are not formed may beused as a viewing side, and since the opening is formed in at least apart of each capsule which is at the substrate side, decrease in imagecontrast caused by gaps formed between the capsules and by the capsulewall films can be dissolved. In this case, on the second substrate,pixel electrodes connected to the switching elements may be provided,and on the first substrate, a counter electrode opposing the pixelelectrodes may be provided. In the structure described above, thecounter electrode is preferably formed of a material havinglight-transmissive properties.

Next, an electronic apparatus of the present invention, which has animage display portion, comprises the above electrophoretic device as theimage display portion. According to this structure, in theelectrophoretic device forming the image display portion, image contrastcan be significantly improved.

Next, a method for manufacturing the electrophoretic device describedabove, comprises: a step of enclosing a dispersion medium andelectrophoretic particles in capsules; and a step of forming an openingportion in at least a part of each of the capsules. In the manufacturingmethod for the electrophoretic device, according to the presentinvention, as described above, since the opening is formed in eachcapsule after the dispersion medium and the electrophoretic particlesare enclosed in the capsules, handling of the dispersion system duringassembly becomes easier. In addition, by forming the opening in eachcapsule, decrease in image contrast caused by gaps formed between thecapsules and by the capsule wall films can be dissolved.

In addition, a method for manufacturing an electrophoretic device,according to the present invention, comprises: a step of enclosing adispersion medium and electrophoretic particles in capsules; a step ofaccommodating the capsules between a first substrate and a secondsubstrate after the enclosure; and a step of forming an opening portionin at least a part of each of the capsules after the accommodation. Inthis case, the capsules may be accommodated together with a bindingagent between the first and the second substrates. As described above,when the binding agent is used, the capsules can be easily accommodatedor disposed, and in addition, the dispersion medium or the like can beprevented from flowing out from the capsules after the openings areformed therein.

Furthermore, a method for manufacturing an electrophoretic device,according to the present invention, comprises: a step of enclosing adispersion medium and electrophoretic particles in capsules; a step ofdisposing the capsules on at least one of a first substrate and a secondsubstrate after the enclosure; a step of forming an opening portion inat least a part of each of the capsules after the disposition; and astep of providing the other substrate on the substrate on which thecapsules are disposed. In this case, the capsules may be disposedtogether with a binding agent on at least one of the first and thesecond substrates. According to the methods described above, theelectrophoretic devices of the present invention can be provided.

In the method described above for manufacturing the electrophoreticdevice, the step of forming the openings in the capsules may comprise anopening step performed by using one or more tools selected among heat,mechanical stress, light, sonic waves, solvents, and corrosive gases. Byusing the tools described above, the openings can be reliably andrapidly formed in the capsules.

In addition, the binding agent may have one or more properties amongvolatility, contractility, plasticity, and flexibility. By using thebinding agent described above, the openings can be reliably formed inthe capsules, and in addition, the image contrast can be furtherimproved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view showing the structure of anelectrophoretic device according to a first embodiment of the presentinvention.

FIG. 2 includes views for illustrating steps of a manufacturing methodfor an electrophoretic device of the present invention.

FIG. 3 includes views showing general examples of an electrophoreticdisplay device, (a) is a cross-sectional view of the structure thereof,and (b) and (c) are views for illustrating an image display principle.

FIG. 4 is a perspective view showing the external structure of anelectronic book as an example of an electronic apparatus of the presentinvention.

FIG. 5 is a block diagram showing the electrical structure of theelectronic book.

FIG. 6 is a perspective view showing the external structure of acomputer as an example of an electronic apparatus of the presentinvention.

FIG. 7 is a perspective view showing the external structure of a mobilephone as an example of an electronic apparatus of the present invention.

FIG. 8 is a perspective view showing the external structure of a digitalstill camera as an example of an electronic apparatus of the presentinvention.

FIG. 9 is a perspective view showing the external structure ofelectronic paper as an example of an electronic apparatus of the presentinvention.

FIG. 10 is a perspective view showing the external structure of anelectronic notebook as an example of an electronic apparatus of thepresent invention.

FIG. 11 is a cross-sectional view showing one modified example of theelectrophoretic device shown in FIG. 1.

FIG. 12 is a cross-sectional view showing another modified example ofthe electrophoretic device shown in FIG. 1.

FIG. 13 is a cross-sectional view showing another modified example ofthe electrophoretic device shown in FIG. 1.

FIG. 14 is a cross-sectional view showing another modified example ofthe electrophoretic device shown in FIG. 1.

FIG. 15 is a cross-sectional view showing an example in which anelectrophoretic device of the present invention is applied to an activematrix electrophoretic display device.

FIG. 16 is a plan view, as is FIG. 15, showing an example in which anelectrophoretic device of the present invention is applied to an activematrix electrophoretic display device.

FIG. 17 is a cross-sectional view showing the structure of amicrocapsule applicable to an electrophoretic display device of thepresent invention.

FIG. 18 is a schematic view showing a part of a manufacturing apparatusfor use in a step of manufacturing the electrophoretic device shown inFIG. 1.

FIG. 19 is a schematic view, as is FIG. 18, showing a part of amanufacturing apparatus.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Next, with reference to drawings, embodiments of the present inventionwill be described. In respective drawings cited in the followingdescription, the same reference numerals of elements in one drawingdesignate the same elements.

Example 1

FIG. 1 is a cross-sectional view showing the structure of a firstembodiment in which an electrophoretic device of the present inventionis applied to an electrophoretic display device. As shown in the figure,an electrophoretic display device 20 of the present invention has afirst substrate 1 and a second substrate 2, and the second substrate 2side is used as an observer side. The second substrate 2 is formed of alight transmissive plate such as a transparent glass or a transparentfilm. On a surface of the second substrate 2 opposing the firstsubstrate 1, a transparent electrode 4 film is formed. The transparentelectrode 4 is formed, for example, of indium tin oxide (ITO) film.

Although being not always necessary to be transparent, the firstsubstrate 1 is formed, for example, of a glass substrate or a filmsubstrate. In addition, on a surface of the first substrate 1 opposingthe second substrate 2, an electrode 3 is formed. Although being notalways necessary to be transparent, the electrode 3 is formed, forexample, of an ITO film.

For ease of illustration in FIG. 1, the electrodes 3 and 4 are each notdivided; however, for example, each of them may be divided into apattern to form a segment type display device. By dividing eachelectrode to form an appropriate pattern, a desired image can bedisplayed.

Between the electrodes 3 and 4, an electrophoretic dispersion 10 isaccommodated together with a binder 41 and microcapsule wall films 40.The electrophoretic dispersion 10 is formed of at least a liquid-phasedispersion medium 6 and electrophoretic particles 5 dispersed in thisliquid-phase dispersion medium 6.

The microcapsule wall film 40 has an opening in the wall film of amicrocapsule in which the electrophoretic dispersion 10 was originally(primarily) enclosed, the opening being formed by an optional tool suchas heat, mechanical stress, light, sonic waves, solvents, or corrosivegases in a part of the wall film which is in contact with the electrode4.

In this embodiment, since an electric field is applied in thelongitudinal direction (direction shown by the arrow in the figure)between the electrode 3 and the electrode 4, and the electrophoreticparticles 5 move in this electric field direction, the structure isformed so that reverse display can be performed.

As described above, since the opening is formed in the wall film of eachmicrocapsule at the observer side, the gaps formed between themicrocapsules can be decreased, and the wall films at the observer sidecan be removed, the image contrast can be significantly improved.

As the liquid-phase dispersion media 6, there may be mentioned alcoholsolvents, such as water, methanol, ethanol, isopropanol, butanol,octanol, and methyl cellusolve; various esters such as ethyl acetate andbutyl acetate; ketones, such as acetone, methyl ethyl ketone, and methylisobutyl ketone; aliphatic hydrocarbons, such as pentane, hexane, andoctane; alicyclic hydrocarbons, such as cyclohexane andmethylcyclohexane; aromatic hydrocarbons including benzene derivativeshaving a long alkyl chain, such as benzene, toluene, xylene,hexylbenzene, heptylbenzene, octylbenzene, nonylbenzene, decylbenzene,undecylbenzene, dodecylbenzene, tridecylbenzene, and tetradecylbenzene;halogenated hydrocarbons, such as methylene chloride, chloroform, carbontetrachloride, and 1,2-dichloroethane; carboxylates; and other variousfatty compounds. Together with a surfactant or the like, these mentionedabove may be used alone or in combination.

In addition, the electrophoretic particle 5 is an organic or inorganicparticle (polymer or colloid) having properties of being moved in adispersion medium by electrophoresis in accordance with a potentialdifference.

As the electrophoretic particles 5, for example, there may be mentionedblack pigments, such as aniline black and carbon black; white pigments,such as titanium dioxide, zinc flower, and antimony trioxide; azo-basedpigments, such as monoazo, disazo, and polyazo compounds; yellowpigments, such as isoindolinone, chrome yellow, iron oxide yellow,cadmium yellow, titanium yellow, and antimony; azo-based pigments, suchas monoazo, disazo, and polyazo compounds; red pigments, such asquinacridone red and chrome vermillion; blue pigments, such asphthalocyanine blue, indanthrene blue, anthraquinone-based dyes, ironblue, ultramarine blue, and cobalt blue; and green pigments such asphthalocyanine green. These mentioned above may be used alone or incombination.

Furthermore, to the pigments described above, whenever necessary, chargecontrol agents in the form of particles composed of electrolytes,surfactants, metallic soaps, resins, rubbers, oils, varnishes, orcompounds; dispersing agents, such as titanium-based coupling agents,aluminum-based coupling agents, and silane-based coupling agents;lubricants; stabilizers; and the like may be added.

As a material for forming the microcapsule wall film 40, for example, agum arabic-gelatin-based composite film, or a compound of a urethaneresin, urea resin, or urea-formaldehyde resin may be used.

As the binder 41, a material having a superior affinity for themicrocapsule wall film 40, adhesion to a base material, and insulatingproperties may be used. For example, preferably used are thermoplasticresins, such as polyethylene, chlorinated polyethylene, ethylene-vinylacetate copolymer, ethylene-ethyl acrylate copolymer, polypropylene, ABSresin, methyl methacrylate resin, vinyl chloride resin, vinylchloride-vinyl acetate copolymer, vinyl chloride-vinylidene chloridecopolymer, vinyl chloride-acrylic acid ester copolymer, vinylchloride-methacrylic acid copolymer, vinyl chloride-acrylonitrilecopolymer, ethylene-vinyl alcohol-vinyl chloride copolymer,propylene-vinyl chloride copolymer, vinylidene chloride resin, vinylacetate resin, poly(vinyl alcohol), poly(vinyl formal), andcellulose-based resin; polymers, such as polyamide resin, polyacetal,polycarbonate, poly(ethylene terephthalate), poly(butyleneterephthalate), poly(phenylene oxide), polysulfone, poly(amide imide),poly(amino bismaleimide), poly(ether sulfone), poly(phenylene sulfone),polyarylate, grafted poly(phenylene ether), poly(ether ether ketone),and poly(ether imide); fluorinated resins, such aspoly(tetrafluoroethylene), poly(fluoroethylene propylene),tetrafluoroethylene-perfluoroalkoxyethylene copolymer,ethylene-tetrafluoroethylene copolymer, poly(vinylidene fluoride),poly(chlorotrifluoroethyelene), and fluorinated rubber; silicon-basedresins, such as organic silicone resin and silicone rubber; and others,such as methacrylic acid-styrene copolymer, polybutylene, and methylmethacrylate-butadiene-styrene copolymer.

In addition, a binding agent used in the electrophoretic device of thepresent invention preferably has one or more features among transparent,tacky, volatile, contractive, plastic, flexible, insulating properties.By using the binding agent having the properties mentioned above, theopening of the microcapsule can be reliably formed, and in addition, theimage contrast can be further improved.

In addition, as for the binding agent, it is preferable that thedielectric constant of an electrophoretic display solution beapproximately equivalent to that of a dispersing agent. Accordingly, forexample, alcohols, ketones, or carboxylic salts are preferably furtheradded to the binder resin composition mentioned above. As the alcoholsmentioned above, 1,2-butanediol, 1,4-butanediol, or the like may beused.

In the electrophoretic display device 20 having the structure describedabove, as shown in FIG. 3(a), the voltage source 9 a or 9 b is appliedbetween the electrodes 3 and 4 by switching the switch 8.

Next, an example of a method for manufacturing an electrophoreticdisplay device having the structure as described above will be describedwith reference to FIG. 2.

As shown in (a) of the same figure, the electrophoretic dispersion 10 isfirst enclosed in a microcapsule 50. As this enclosing step, a knownmicrocapsule forming technique, such as interfacial polymerization,in-situ polymerization, phase separation, interfacial precipitation, orspray drying, may be used.

In this enclosing step, a wall film material is optionally selected inconsideration of a wall film opening technique performed in a subsequentstep. For example, in the case in which the opening is performed byusing heat or light, a material having a solubility enhanced by heat orlight may be selected; in the case in which the opening is performed byusing mechanical stress or sonic wave, a material having appropriatelyweak mechanical strength is selected; in the case in which an openingtechnique using a solvent is employed, a material soluble in a solventto be used is selected; and in addition, in the case in which an openingtechnique using a corrosive gas is employed, a material which iscorroded by a gas to be used is selected.

Subsequently, a number of the microcapsules 50 formed as described aboveare mixed with a binding agent 51, and in addition, when it is desired,a dielectric constant adjuster may also be added thereto. Next, as shownin (b) of the same figure, the resin composition (emulsion or solutioncontaining an organic solvent) thus formed is applied onto the electrode3 by a known coating method, such as a roller coating method, rollerlamination method, screen printing method, spray method, or ink-jetmethod.

In the step described above, the binding agent 51 having suitableproperties is selected in consideration of a binder contractiontechnique performed in a subsequent step. For example, in the case inwhich the contraction is performed by evaporation of a solvent, amaterial having volatility is selected; in the case in which thecontraction is performed by using heat or light, a material havingheat-shrinkable or light-shrinkable properties is selected; and in thecase in which the contraction is performed by using a mechanical stress,a material having plasticity is selected.

Next, as shown in (c) of the same figure, in a part of the wall film ofeach microcapsule 50, which is at the side opposite to the electrode 3,openings are formed by various technique as described below. As thetechnique for forming the openings in the wall films, in accordance witha material for the microcapsule 50, an optional technique using, forexample, heat, mechanical stress, light, sonic waves, solvents, orcorrosive gas, may be used. For example, FIG. 17 is a schematic viewshowing a step in which the openings are mechanically formed in the wallfilms of the microcapsules 50 by needle-shaped projections 231. FIG. 18is a schematic view showing a step in which the openings are formed byheat application. In this case, the microcapsules 50 are each heatedpartly by a heater 241 provided with a resistive heating wire 242.

Next, as shown in (d) of the same figure, by an appropriate technique,the binding agent 51 is contracted. In this step, as a tool forperforming this contraction, in accordance with a material for formingthe binding agent 51, volatility of a solvent, heat, mechanical stress,or the like is used. In this contraction step, since an opening areaformed in the wall film of each microcapsule 50 is largely expanded, thewall films at the observer side are removed, and in addition, the gapsbetween the microcapsules are decreased, resulting in significantimprovement in image contrast.

In the step described above, the step of forming the opening in the wallfilm of each microcapsule 50 and the step of performing the contractionof the binding agent 51 may be simultaneously performed. In this case, atechnique used for the opening-forming step for the wall film ispreferably the same as that used for the contraction step.

In addition, in this contraction step, the microcapsules 50 may bedeformed. In particular, when the microcapsule wall films at theelectrode 3 side are flattened by the contraction of the binding agent51 provided in the vicinity of the electrode, it is preferable in termsof the improvement in image contrast.

As shown in (e) of the same figure, the second substrate 2 is finallyprovided (laminated) on a large number of the microcapsules 50 so thatthe electrode 4 is located at the microcapsules 50 side. In this step,in order to prevent the electrode 4 and the electrophoretic dispersion10 from being brought into direct contact with each other, an insulatingfilm may be formed on the surface of the electrode 4.

Example 2

Next, a method for manufacturing an electrophoretic device according toa second embodiment of the present invention will be described. In thefirst embodiment, after the microcapsules 50 and the binding agent 51are provided on the electrode 3, the opening-forming step for the wallfilms of the microcapsules and the contraction step for the bindingagent 51 are performed, and the electrode 4 is then provided.

However, in this second embodiment, the microcapsules 50 and the bindingagent 51 are accommodated beforehand between the electrodes 3 and 4, andin the state described above, the opening-forming step for the wall filmof the microcapsule and the contraction step for the binding agent areperformed. In this manufacturing method, the opening-forming techniquemay use heat, mechanical stress, light, sonic waves, or the like, andthe contraction technique may use heat, mechanical stress, light, or thelike.

According to this second embodiment, prior to the opening-forming stepfor the microcapsule wall film and the contraction step for the bindingagent, since the microcapsules and the binding agent are accommodatedbetween the electrodes, leakage of the dispersion and intrusion ofimpurities can be avoided.

Next, the structure of an electronic book, which is an embodiment of anelectronic apparatus according to the present invention, will bedescribed with reference to FIG. 4. This electronic book 61 is formed sothat data of books of electronic publication, the data being stored inmemory media such as CDROM's, is displayed on a display screen of adisplay device for reading, and as the display device therefor, theelectrophoretic display device described above is used. Accordingly, asshown in FIG. 4, the electronic book 61 has a book-shaped frame 62 and acover 63 which is capable of opening and closing and which is providedon this frame 62. On the frame 62, there are provided an operationportion 65 and a display device 64 having a display surface in anexposed state on a surface thereof.

Inside the frame 62, as shown in FIG. 5, there are provided a controller36, a counter 37, a memory 38, a data reader (not shown in the figure)for reading data in a memory medium such as a CDROM, and the like.

The display device 64 according to this embodiment comprises a pixelportion 69 having the structure formed of the electrophoretic displaydevice 20 as shown in FIG. 1, and peripheral circuits 70 which areprovided together with the pixel portion 69 and which are integrated. Inthe peripheral circuits 70, a decoder type scan driver and data driverare provided.

As long as being provided with the display device 64 having thestructure formed of the electrophoretic display device, the electronicapparatus of the present invention is not limited to the electronic bookdescribed in the above embodiment. Hereinafter, some other examples ofthe electronic apparatuses provided with this display device 64 will bedescribed.

<Mobile Computer>

An example in which the display device 64 described above is applied toa display portion of a mobile computer will first be described. FIG. 6is a perspective view showing the structure of this personal computer.As shown in FIG. 6, a personal computer 80 is formed of a main body 82including a keyboard 81, and a display unit including the display device64 described above.

<Mobile Phone>

Next, an example in which the display device 64 described above isapplied to a display portion of a mobile phone will be described. FIG. 7is a perspective view showing the structure of this mobile phone. Asshown in FIG. 7, in addition to a plurality of operation buttons 91,this mobile phone 90 includes the display device 64 described abovetogether with an earpiece 92 and mouthpiece 93.

<Digital Still Camera>

Furthermore, an example in which the display device 64 described aboveis used as a viewfinder for a digital still camera will be described.FIG. 8 is a perspective view showing the structure of this digital stillcamera, and in addition, connections with external apparatuses are alsoshown briefly.

Although general cameras expose films by light images of objects, adigital still camera 100 generates an image signal by photoelectricconversion of a light image of an object using an imaging device such asa CCD (Charged Coupled Device).

On the rear surface of a case 101 of the digital still camera 100, thedisplay device 64 described above is provided, and display is performedin accordance with image signals supplied by the CCD. Accordingly, thedisplay device 64 serves as a viewfinder for displaying an object. Inaddition, at the observer side (rear surface side in the figure) of thecase 101, a light-receiving unit 102 including optical lenses, the CCD,and the like is provided.

When a picture taker recognizes an object image displayed in the displaydevice 64 and then presses a shutter button 103, an image signal of theCCD at the same time is transferred to and stored in a memory of acircuit board 104.

In this digital still camera 100, on the side surface of the case 101, avideo signal output terminal 105 and a data communication input-outputterminal 106 are provided. In addition, as shown in the figure, theformer, the video signal output terminal 105, and the latter, the datacommunication input-output terminal 106, are connected to a televisionmonitor 108 and a personal computer 108, respectively, when necessary.In addition, in response to predetermined operations, the image signalstored in the memory of the circuit substrate 104 is output to thetelevision monitor 107 or the personal computer 108.

<Electronic Paper>

Next, an example in which the display device 64 described above isapplied to a display portion of electronic paper will be described. FIG.9 is a perspective view showing the structure of this electronic paper.This electronic paper 110 is formed of a main body 111, which iscomposed of a rewritable sheet having the texture and flexibilitysimilar to those of paper, and a display unit incorporating the displaydevice 64 described above.

<Electronic Note>

In addition, FIG. 10 is a perspective view showing the structure of anelectronic notebook. As shown in FIG. 10, this electronic notebook 120comprises a stack of electronic paper 110 shown in FIG. 9 and a cover121 which is folded in half so as to sandwich the stack of electronicpaper 110. When the cover 121 is provided with display data input means,the display content can be changed while the electronic paper is in astacked state.

As described above, according to the embodiments of the electronicapparatuses of the present invention, as the display device 64, anelectrophoretic display device as shown in FIG. 1 is used. As a result,although the electrophoretic display device is used, a display devicehaving significantly improved image contrast can be obtained.

As the electronic apparatuses described above, in addition to theelectronic book in FIG. 4, the personal computer in FIG. 6, the mobilephone in FIG. 7, the digital still camera in FIG. 8, and the electronicpaper in FIG. 9, for example, there may be mentioned liquid crystaltelevisions, viewfinder type and direct viewing type video taperecorders, car navigation apparatuses, pagers, electronic pocketbooks,electronic calculators, word processors, workstations, televisionphones, POS terminals, and apparatuses provided with touché panels. Inaddition, as display portions of the electronic apparatuses mentionedabove, the above display device may be naturally used.

Next, a modified example of the structure of the electrophoretic displaydevice shown in FIG. 1 will be described.

FIG. 11 is a view showing an example of an electrophoretic devicecomprising microcapsules 40 a each having an opening portion at thesecond substrate 2 side as in the case shown in FIG. 1, microcapsules 40b each having an opening portion facing in a perpendicular directionwith respect to the substrates 1 and 2, and microcapsules 40 c eachhaving opening portions at both the first substrate 1 and the secondsubstrate 2 sides. As described above, in the electrophoretic device,when each microcapsule has an opening portion formed in at least a partthereof, the gap between the microcapsules is decreased at that partmentioned above, and hence at least the contrast decrease can be avoidedor suppressed. In this case, as in the example shown in FIG. 1, it isassumed that the electric field is applied in a longitudinal direction,and the electrophoretic particles 5 are moved in the longitudinaldirection.

FIG. 12 is a view showing an example of an electrophoretic devicecomprising microcapsules 40 b each having an opening portion facing inthe perpendicular direction with respect to the substrates 1 and 2. Inthis case, for example, in an electrophoretic device in which a lateralelectric field is applied, since resistance components are decreased atleast at the opening portions facing in the lateral direction, voltageapplication can be advantageously performed. In the example shown inFIG. 12, it is assumed that the electric field is applied in the lateraldirection (direction indicated by the arrow in the figure) between theelectrodes 3 a and 3 b formed on the first substrate 1, and theelectrophoretic particles 5 are moved in the lateral direction.

As shown in FIG. 13, an electrophoretic device comprising themicrocapsules 40 c each having opening portions at the first and thesecond substrate 1 and 2 sides may also be formed. In addition, thestructure in which an insulating film is provided between the openingportions and the electrode 3 or 4 may also be formed. In this case,adhesion of the electrophoretic particles 5 to the electrode 3 or 4 canbe avoided.

In addition, as shown in FIG. 14, an insulating layer 11 may be providedbetween the opening portions and the electrode (the electrode 4 in FIG.14) at which the opening portions exist. In this case, adhesion of theelectrophoretic particles 5 to the electrode at which the openingportions exist can be avoided or suppressed.

Next, an embodiment in which the electrophoretic device of the presentinvention is applied to an active matrix electrophoretic display devicewill be described. FIG. 16 is a plan view showing an electrophoreticdisplay device. In addition, FIG. 15 is a view showing thecross-sectional structure taken along the line A-A′ in FIG. 16.

An electrophoretic device 20B shown in these figures is formed of thefirst substrate 1, the second substrate 2 disposed to oppose thereto,and an electrophoretic layer (electrooptic layer) 21 providedtherebetween. At the internal surface side of the second substrate 2 (atthe electrooptic layer 21 side), a color filter layer 12, a commonelectrode 4, and an insulating layer 11 are formed. At the internalsurface side of the first substrate 1 (at the electrooptic layer 21side), an elemental portion 27 including a plurality of pixel electrodes3 and the like is formed. At the second substrate 2 side, the secondsubstrate 2, the common electrode 4, and the insulating layer 11 havelight transmissive properties, and the external surface of the secondsubstrate 2 serves as a display surface of this electrophoretic device20B. Although not shown in the figure, on the first substrate 1 havingthe elemental portion 27, various peripheral circuits for driving andcontrolling the elemental portion 27 may be formed. In addition, in thisembodiment, the common electrode 4 is formed at the second substrate 2side, and the elemental portion 27 is formed at the first substrate 1side; however, the elemental portion 27 may be formed at the secondsubstrate 2 side.

The second substrate 2 may be formed of a substrate having lighttransparency such as a transparent glass or film. Although not beingnecessary to be transparent, the first substrate 1 may be formed, forexample, of a glass substrate or resin film. In addition, the colorfilter layer 12 has the structure including color layers (R, G, B)corresponding to red, blue, and green, and BM layers provided betweenthe respective color layers (R, G, B). In addition, the insulating layer11 is primarily formed of a transparent, insulating film including SiO₂or the like.

As shown in FIG. 15, the electrophoretic layer 21 has the structure inwhich a plurality of the electrophoretic particles 5 are dispersed inthe dispersing medium 6 accommodated in the microcapsules 50. Themicrocapsules 50 have the opening portions provided at the insulatinglayer 11 side. In more particular, the opening portions of themicrocapsules are formed so as to be in contact with the insulatinglayer 11, that is, the openings are provided in the electric fielddirection (direction indicated by the arrow in the figure) of theelectrophoretic display device 20B. Concerning the dispersion medium 6and the electrophoretic particles 5, the same configurations as thoseused in the electrophoretic display device of the embodiment shown inFIG. 1 may be used.

FIG. 16 is a plan view showing a plurality of the pixel portions 17(pixel electrodes 3 and TFT elements 13), data lines 16, scanning lines14, and the like, which are arranged in a matrix and which form an imagedisplay region of the electrophoretic display device 20B of thisembodiment. According to the electrophoretic display device 20B of thisembodiment, in each of a plurality of display units which are arrangedin a matrix and which form the image display region, there are providedthe pixel electrode 3 functioning as a transparent conductive layer andthe TFT element 13 for controlling electricity supplied to the pixelelectrode 3, and the data line 16 to which an image signal is suppliedis electrically connected to the source of the TFT element 13. The imagesignals to be stored in the data lines 16 are supplied in aline-sequential manner thereto or are supplied to each group formed of aplurality of neighboring data lines 16.

In addition, as shown in FIG. 15, the scanning lines 14 are electricallyconnected to the gates of the TFT elements 13, and scanning signals areapplied pulsewise in a line-sequential manner to the plurality of thescanning lines 14 with predetermined timing. In addition, the pixelelectrodes 3 are electrically connected to the drain electrodes 19 ofthe TFT elements 13, and by placing the TFT elements 13 in an ON-statefor a predetermined period of time, image signals are stored, which aresupplied from the data lines 16, with predetermined timing. An imagesignal having a certain level stored in the pixel electrode 3 ismaintained with the common electrode 4 for a predetermined period oftime. The electrophoretic particles 5 having charges are attracted toone of the pixel electrode 3 and the common electrode 4, whichever has apolarity opposite to that of the particles, and hence grayshade displaycan be performed by the contrast between the charged particle color andthe dispersion medium color.

As shown in FIG. 16, on the first substrate 1, a plurality of the pixelelectrodes 3 is provided in a matrix, and the data lines 16 and thescanning lines 14 are provided along the longitudinal and lateralboundaries of pixel electrodes 3, respectively. In this embodiment,display areas formed in regions surrounded by the data lines 16 and thescanning lines 14 are display units (dots), the configuration is formedso that display can be performed in each of the display units arrangedin a matrix, and a plurality of the microcapsules 50 is provided in eachdot.

Next, the structure of the microcapsule 50 applicable to the embodimentsdescribed above will be described. FIG. 17 is a cross-sectional view ofa microcapsule having the structure in which the capsule wall film 40,and the dispersion medium 6 and the electrophoretic particles 5, whichare filled inside the wall film 40, are provided. The dispersion medium6 is formed including a coloring material, and the coloring materialcontained in the dispersion medium 6 filled inside the wall film maycolor the wall film 40.

When the microcapsules 50 described above, each having an opening in atleast a part thereof, are provided in an electrophoretic display device,the electrophoretic display devices of the embodiment described abovecan be provided.

Advantages

As has thus been described, the electrophoretic device of the presentinvention comprises the plurality of the capsules which contain thedispersion medium and the electrophoretic particles and which areprovided between the first substrate and the second substrate, whereineach capsule has an opening formed in at least a part thereof.Accordingly, the resistance component at the opening portion isdecreased, and an effect of advantageously applying voltage can beobtained. In addition, since gaps formed between the capsules areunlikely to be formed at least at the opening portions, an advantage ofimprovement in image contrast can be obtained.

1. A method for manufacturing an electrophoretic device, comprising: a step of enclosing a dispersion medium and electrophoretic particles in capsules; and a step of forming an opening portion in at least a part of each of the capsules.
 2. A method for manufacturing an electrophoretic device, comprising: a step of enclosing a dispersion medium and electrophoretic particles in capsules; a step of accommodating the capsules between a first substrate and a second substrate after the enclosing step; and a step of forming an opening portion in at least a part of each of the capsules after the accommodating step.
 3. A method for manufacturing an electrophoretic device, according to claim 2, wherein the capsules are accommodated with a binding agent between the first substrate and the second substrate.
 4. A method for manufacturing an electrophoretic device, comprising: a step of enclosing a dispersion medium and electrophoretic particles in capsules; a step of disposing the capsules on at least one of a first substrate and a second substrate after the enclosing step; a step of forming an opening portion in at least a part of each of the capsules after the disposing step; and a step of providing the other of the first and second substrate on the at lest one substrate on which the capsules are disposed.
 5. A method for manufacturing an electrophoretic device, according to claim 4, wherein the capsules are disposed together with a binding agent on at least one of the first substrate and the second substrate.
 6. A method for manufacturing an electrophoretic device, according to claim 4, wherein the step of forming the opening portion comprises an opening step performed by using at least one of the group selected from heat, mechanical stress, light, sonic waves, solvents, and corrosive gases.
 7. A method for manufacturing an electrophoretic device, according to claim 6, wherein the binding agent has at least one property selected form the group of volatility, contractility, plasticity, and flexibility. 